Fast cache purge in content delivery network

ABSTRACT

Processing a purge request is disclosed. The purge request is received. An availability state for each content distribution node in a group of content distribution nodes is tracked. Based on the purge request, one or more purge instructions are generated for one or more available state content distribution nodes of the group. Based on the purge request, one or more queued purge instructions are queued for one or more unavailable state content distribution nodes of the group. It is determined that the one or more available state content distribution nodes of the group have completed processing the one or more purge instructions generated for the one or more available state content distribution nodes. Based at least in part on the queuing of the one or more queued purge instructions for the one or more unavailable state nodes, an indication that the purge request has been completed is authorized.

BACKGROUND OF THE INVENTION

Traditionally purging (e.g., removing or modifying) stored contentserved by a content delivery network (CDN) can often take up to 24hours. In order to confirm that an indicated content has been purgedacross the entire CDN, a purge request must be propagated out to theentire CDN network and a confirmation of completion of the purge request(e.g., confirmation that the indicated content of the purge request hasbeen removed from the local storage/cache of the node) must be receivedfrom every content delivery node of the CDN. In CDNs with a large numberof nodes, it is likely that some of the nodes are temporarilyunreachable for a few seconds to a few hours at various different timesdue to maintenance, upgrades, and/or errors. If a node is unavailable,the desired content purge cannot be completed and confirmed until thenode becomes available again to process the purge request. Often otherprocesses and services cannot proceed until a confirmation of thedesired content purge is received. Therefore, there exists a need toreduce the amount of time required to confirm a purge of desiredcontent.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a block diagram illustrating an embodiment of a contentdistribution network environment.

FIG. 2 is a flowchart illustrating an embodiment of a process forprocessing a purge request.

FIG. 3 is a flowchart illustrating an embodiment of a process fordetermining a status of a purge request.

FIG. 4 is a flowchart illustrating an embodiment of a process forupdating a status of a node as unavailable.

FIG. 5 is a flowchart illustrating an embodiment of a process forupdating a status of a node as available.

FIG. 6 is a flowchart illustrating an embodiment of a process forprocessing a purge instruction.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

A content distribution network manager is disclosed. In someembodiments, a purge request is received from a client. For example, arequest to remove and/or update an indicated content being provided viaa content distribution network is received from a content provider thatinitially provided the indicated content to be served to users by thecontent distribution network. One or more purge instructions aregenerated for one or more available content distribution nodes of acontent distribution network. For example, an instruction to purge anindicated content is provided to content distribution nodes that areonline and available to receive the instruction. In some embodiments, itis determined that the one or more available content distribution nodeshave completed processing the one or more generated purge instructions.One or more purge instructions are queued for one or more unavailablecontent distribution nodes of the content distribution network. Forexample, the purge instruction is placed in each purge instruction queueassociated with each unavailable offline node to allow the unavailablenode to process the queued purge instruction when the unavailable nodebecomes available. An indication is authorized to provide that the purgerequest has been completed based on the queued instruction(s) for theone or more unavailable nodes. For example, it is indicated that thepurge request has been completed even though the unavailable nodes havenot processed purge instruction in their queues because the unavailablenodes will process the queued purge instructions before the unavailablenodes can become available to serve content.

FIG. 1 is a block diagram illustrating an embodiment of a contentdistribution network environment. Client 102 communicates with contentdistribution manager 106 via network 104. In some embodiments, client102 provides a request to purge a specified content beingserved/distributed by a content distribution network. For example,client 102 sends an instruction using an Application ProgrammingInterface (API) of manager 106, and the instruction specifies a contentto be purged (e.g., specified content to be removed and/or replaced fromthe content distribution network). Examples of client 102 include aserver, a system, a device, and any other computer able to instructcontent distribution manager 106. Client 102 may be a part of an originserver that initially provided the indicated content to be purged to thecontent distribution network. Content distribution manager 106 managespurging of the specified content served by a content distributionnetwork. The content distribution network includes one or moredistributed systems that provide content to one or more users via anetwork. For example, the content distribution network includes one ormore nodes and systems of a CDN. In the example shown, nodes 112, 114,and 116 are included in a content distribution network. Nodes 112, 114,and 116 may be edge nodes of a CDN or load balanced servers of a serverfarm. Nodes 112, 114, and 116 may be content distribution nodes that areeach able to distribute mirrored content from its local storage/cache.For example, nodes 112, 114, and 116 are each located in differentgeographical locations and provide the same content to users near thegeographical location of each node to minimize delay associated withproviding content from servers located geographically far away. Nodes112, 114, and 116 may be each associated with a local cache/storagewhere content to be served/provided by the node is stored. Each localcache/storage may be included in each node or connected to each node viaa networked or direct connection.

Content distribution manager 106 communicates with nodes 112, 114, and116 via network 110. Network 104 and network 110 may be the same networkor different networks. For example, network 110 and network 104 are boththe Internet. In another example, network 104 is the Internet andnetwork 110 is a local area network. Content distribution manager 106may include one or more devices and servers. Content distributionmanager 106 maintains an availability status (e.g., whether a node isonline, offline, or in a transitional state) of each node of the contentdistribution network managed by content distribution manager 106. Thestatus may be updated by manager 106 and/or directly by a node. Thestatus may be stored in storage 108. Examples of storage 108 include adatabase, a table, a hash table, a list, a memory, and any other datastructure or device configured to store data. Storage 108 may beconnected to manager 106 directly, via network 104 and/or network 110.Content distribution manager 106 maintains a separate purge instructionqueue for each node of the content distribution network maintained bymanager 106. The queue includes purge instructions ready to be providedto an associated node when the node is ready to receive the instruction.For example, if a node is unavailable, the queue stores queued purgeinstructions ready to be provided to the node when the node becomesavailable again. The queue for each node may be stored in storage 108and/or another storage/data structure of manager 106. For each receivedpurge request, manager 106 adds in each purge instruction queue of thecontent distribution nodes of the content distribution network to bepurged, a corresponding instruction to purge the specified content ofthe purge request from the cache/storage of each node.

One or more of the following may be included in networks 104 and 110: adirect or indirect physical communication connection, mobilecommunication network, Internet, intranet, Local Area Network, Wide AreaNetwork, Storage Area Network, a wireless network, a cellular network,and any other form of connecting two or more systems, communicationdevices, components, or storage devices together. Although exampleinstances of components have been shown to simplify the diagram,additional instances of any of the components shown in FIG. 1 may exist.Any of the components shown in FIG. 1 may be physically integrated in asingle hardware component or may represent a plurality of hardwarecomponents. Components not shown in FIG. 1 may also exist. Manager 106and/storage 108 may be one of a plurality of replicated/redundantsystems and/or devices.

FIG. 2 is a flowchart illustrating an embodiment of a process forprocessing a purge request. The process of FIG. 2 may be at least inpart implemented on content distribution manager 106 of FIG. 1.

At 202, a purge request is received. The purge request may specify thatcontent is to be removed and/or updated from cache/storage of contentdistribution nodes of a content distribution network. The contentdistribution network may include one or more nodes that mirror contentand provide content to various users that may be able to obtain contentfaster from one content distribution node over another node. In someembodiments, the purge request is received from a content provider suchas an origin server that provides content to be served/distributed by acontent distribution network (e.g., CDN). For example, the purge requestis received from client 102 at content distribution manager 106 ofFIG. 1. In some embodiments, the purge request is received from a userthat accesses a receiver of the purge request via an interface providedby the receiver. For example, content distribution manager 106 of FIG. 1provides a web interface to allow an authorized user to provide thepurge request. In some embodiments, the purge request has been providedusing an API of the receiver of the purge request. The purge request mayidentify the content (e.g., content location address) to be purged. Forexample, the purge request identifies one or more uniform resourceidentifiers (URIs) and/or uniform resource locators (URLs) of thecontent to be purged. The purge request may be encrypted.

In some embodiments, the received purge request is verified. Forexample, verification is performed to determine whether a requestor ofthe purge request is authorized to provide a request to purge anidentified content of the purge request. If the purge request isdetermined as unauthorized, the process may end and an error message maybe sent to the requestor.

At 204, one or more purge instructions based on the request are queuedfor each node to be purged. In some embodiments, the nodes to be purgedinclude all member content distribution nodes (e.g., edge nodes) of acontent distribution network. In some embodiments, the nodes to bepurged may be identified in a listing stored by a content distributionmanager such as manager 106 of FIG. 1. The list of nodes to be purged(e.g., list of content distribution nodes of a content distributionnetwork) may be dynamically generated and/or statically configured. Thelist may also be updated (e.g., automatically updated, dynamicallydetermined, and/or manually configured) as nodes of a contentdistribution network are removed and/or added. In some embodiments, acontent distribution manager may mange a plurality of contentdistribution networks, the content distribution network associated withthe request is determined, and the nodes of the determined distributionnetwork are selected as the nodes to be purged.

In some embodiments, each node to be purged is associated with aseparate queue that may include one or more queued purge instructions.The purge instruction based on the purge request instructs a node topurge (e.g., remove or update) a specified content of the purge requestfrom a storage of the node. The queues of the nodes of a contentdistribution network are stored and/or managed by a content distributionmanager (e.g., manager 106 of FIG. 1). In some embodiments, the queuesare managed using Advanced Message Queuing Protocol (AMQP). For example,RabbitMQ software is utilized to implement and manage the queues. Thequeue of each node managed by the content distribution manager may beconfigured as a first-in-first-out (FIFO) queue. For example, the oldestpurge instruction entry is removed for processing before newer entries.In some embodiments, when a purge instruction is placed in the queue,the purge instruction is associated with a time value (e.g., timestamp).

The nodes to be purged may be in different availability states. Forexample, a node that is functioning normally and available toserve/distribute content to users is in an available state (e.g., onlinestatus), a node that is not available to serve/distribute content tousers is in an unavailable state (e.g., offline status), and apreviously unavailable node that is in the process of becoming availableis in a transition state (e.g., ready-to-be-online status). Theavailability state of each node of a content distribution network may betracked by the content distribution manager. For example, the contentdistribution manager detects and updates a listing (e.g., stored instorage 108 of FIG. 1) of the availability state of each node.

When a node of a content distribution network is available (e.g.,online), it actively processes purge instructions stored in its queue.For example, each online node periodically checks whether any purgeinstructions are stored in its queue and requests purge instructionsfrom its queue (e.g., in FIFO order) one by one for processing. When anode is not available (e.g., offline), the queue of the node storesqueued purge instructions to allow the node to process the queued purgeinstructions when the node becomes available to process theinstructions. A purge instruction implementing the received purgerequest is placed in each queue of content distribution nodes of acontent distribution network to be purged. In an alternative embodiment,if a node is available, the purge instruction may be directly issued tothe node without storing the purge instruction in a queue.

At 206, it is verified that all available nodes have purged theirstorage with respect to the purge request. In some embodiments, when anode successfully processes a provided purge instruction (e.g., clearspecified content from local storage/cache of the node), the nodeprovides a confirmation that the purge instruction has been successfullyprocessed by the node. This confirmation may be received by the contentdistribution manager and the manager tracks whether the purgeinstructions of a specific purge request have been successfullycompleted (e.g., tracked using storage 108 of FIG. 1). In someembodiments, it is verified that all available nodes purged theirstorage with respect to the purge request if all nodes of a contentdistribution network that are indicated to be available (e.g., online)have provided a confirmation that a provided purge instructioncorresponding to the purge request has been successfully completed.

At 208, a confirmation is provided that the purge request has beensuccessfully completed. For example, a provider of the purge request isprovided an indication that the indicated content to be purged in therequest will effectively no longer be provided by a content distributionnetwork. This confirmation may allow the receiver of the confirmation toimplement a change, a process, a service, an update, and/or an upgradethat relies on the indicated content of the request to be no longerprovided by the content distribution network. In some embodiments, theconfirmation may be provided even though unavailable nodes (e.g.,offline nodes) have not purged their individual cache/storage byprocessing the purge instructions corresponding to the purge requestbecause each unavailable node is configured to process the purgeinstruction in its queue before the unavailable node becomes available.In some embodiments, the confirmation is only provided if theverification of 206 is made and it is verified that a purge instructioncorresponding to the purge request has been successfully added to eachqueue of any nodes that are unavailable. In some embodiments, theconfirmation is only provided if the verification of 206 is made, it isverified that all transitional nodes purged their storage with respectto the purge request (e.g., successfully completed the purge instructioncorresponding to the purge request), and it is verified that a purgeinstruction corresponding to the purge request has been successfullyadded to each queue of any nodes that are unavailable.

FIG. 3 is a flowchart illustrating an embodiment of a process fordetermining a status of a purge request. The process of FIG. 3 may be atleast in part implemented on content distribution manager 106 of FIG. 1.In some embodiments, at least a portion of the process of FIG. 3 isincluded in 206 and/or 208 of FIG. 2.

At 302, it is verified that all purge instructions corresponding to apurge request have been added to each queue for at least eachunavailable node of a content distribution network. In some embodiments,the purge request is the purge request received in 202 of FIG. 2 and thequeue is the queue utilized in 204 of FIG. 2. In some embodiments, acontent distribution manager (e.g., manager 106 of FIG. 1) tracks anavailability state (e.g., a node can be either in available,unavailable, or transitional state) of each content distribution node ofthe content distribution network. In some embodiments, for each trackednode that is known to be in an unavailable state (e.g., offline statusand not available to serve content to requestors), it is verified that apurge instruction implementing the purge request has been added to theunavailable node's purge instruction queue. In some embodiments, foreach purge request, statuses of the purge instructions corresponding tothe purge request are tracked, and for each node that is identified tobe in an unavailable state, the purge instruction status of the nodeidentifies whether the purge instruction of the purge request has beenadded to the node's queue. When the purge instruction is added to aqueue of a node, the purge instruction status of each node is updated toidentify that the instruction has been added, and the verification of302 may be performed by checking this purge instruction status of nodesthat are indicated to be in an unavailable state. In some embodiments,the verification of 302 may be made as a confirmation that unavailablenodes have completed the purge instruction even though unavailable nodeshave not purged their storage by processing the purge instructions intheir queues because each node is configured to process required purgeinstructions before the unavailable node becomes available.

At 304, it is verified that all purge instructions corresponding to thepurge request have been successfully completed for at least eachavailable node of the content distribution network. In some embodiments,for each node of the content distribution network that is known to be inan available state (e.g., online and ready to serve/distribute cachedcontent), it is verified that the purge instruction has beensuccessfully processed and completed (e.g., content indicated by theinstruction has been purged by the node). If the purge instruction hasnot been completed for an available node, the process waits until thepurge instruction has been completed by the node before providing theverification in 304. In some embodiments, for each purge request,statuses of the purge instructions corresponding to the purge requestare tracked, and for each node that is identified to be in an availablestate, the purge instruction status of the node identifies whether aconfirmation has been received that the purge instruction of the purgerequest has been successfully completed by the node. For example, when anode obtains a purge instruction from its queue and successfullyprocesses the purge instruction, the node provides a notification thatthe purge instruction has been completed to a content distributionmanager that tracks the completion of purge instructions. When the purgeinstruction has been successfully completed by a node, the purgeinstruction status of the node for the particular purge request isupdated to identify that the instruction has been completed, and theverification of 304 may be performed by checking the purge instructionstatus of nodes that are indicated to be in an available state.

At 306, it is verified that all purge instructions corresponding to thepurge request have been successfully completed for at least each node ofthe content distribution network that is in a transitional state. Insome embodiments, for each node of the content distribution network thatis known to be in the transitional state (e.g., node is not currentlyserving/distributing stored content as an available node, but the nodeis preparing (e.g., processing purge instructions in its queue) tobecome an available node), it is verified that the purge instruction hasbeen successfully completed. If the purge instruction has not beencompleted by a transitional node, the process waits until the purgeinstruction has been completed before providing the verification in 306.In some embodiments, for each purge request, statuses of the purgeinstructions corresponding to the purge request are tracked, and foreach node that is identified to be in a transitional state, the purgeinstruction status of the node identifies whether a confirmation hasbeen received that the purge instruction of the purge request has beensuccessfully completed by the node. For example, when a node obtains apurge instruction from its queue and successfully processes the purgeinstruction, the node provides a notification that the purge instructionhas been completed to a content distribution manager that tracks thecompletion of purge instructions. When the purge instruction has beensuccessfully completed by a node, the purge instruction status of thenode for the particular purge request is updated to identify that theinstruction has been completed, and the verification of 306 may beperformed by checking the purge instruction status of nodes that areindicated to be in a transitional state. In an alternative embodiment,step 306 is optional.

At 308 it is determined that a purge complete indication may be providedwith respect to the purge request. In some embodiments, thedetermination of 308 is only made if the verifications have beensuccessfully completed for steps 302, 304, and 306. In some embodiments,the determination of 308 is only made if the verifications have beensuccessfully completed for at least steps 302 and 304. The determinationin 308 may allow the confirmation to be provided in 208 of FIG. 2.

FIG. 4 is a flowchart illustrating an embodiment of a process forupdating a status of a node as unavailable. The process of FIG. 4 may beat least in part implemented on content distribution manager 106 of FIG.1.

At 402, an indication is received that a node is unavailable. The nodemay be unavailable because the node has encountered an error, is beingupgraded, is being updated, is being maintained, etc. In someembodiments, the node is a content distribution node (e.g., edge node)of a content distribution network. An unavailable node may be notavailable to serve/distribute content. The indication may be received bya content distribution manager that tracks an availability state of thenode. In some embodiments, the indication is received from the node. Forexample, the node provides a message that the node has encountered anerror and/or will become unavailable (e.g., due to upgrade, update,etc.). In some embodiments, the indication is received if the node doesnot provide a message. For example, the node provides a heartbeatmessage periodically and the indication is received if the heartbeatmessage has not been received within a period amount of time. In anotherexample, the content distribution manager periodically sends a statusinquiry message to the node and the indication is received if the nodedoes not respond to the status inquiry message.

At 404, an availability state of the node is indicated as unavailable.For example, a stored status indicator of the node is updated as“offline.” In some embodiments, indicating the state includes modifyinga data structure of a content distribution manager that tracks theavailability state of nodes of a content distribution network. Forexample, a list entry corresponding to the node is updated to indicatethat the node is unavailable. The state indicated in 404 may be used in302 of FIG. 3 to at least in part determine whether the node isunavailable.

FIG. 5 is a flowchart illustrating an embodiment of a process forupdating a status of a node as available. The process of FIG. 5 may beat least in part implemented on content distribution manager 106 of FIG.1.

At 502, a request for a next purge instruction from a queue of a nodethat is indicated to be unavailable is received. In some embodiments,the next purge instruction from the queue is the purge instruction addedto the queue in 204 of FIG. 2. In some embodiments, the request isreceived from the node that is indicated to be in an unavailable state.For example, the node was previously indicated to be unavailable in 404of FIG. 4, and the node has provided the request for the next purgeinstruction in order to process a backlog of one or more purgeinstructions in its queue in preparation to become available again toserve/distribute content as a part of a content distribution network.

At 504 it is determined whether an unprocessed purge instruction existsin the queue and whether a time value associated with the next purgeinstruction, if applicable, is chronologically before a threshold time.For example, it is determined whether any purge instruction is left inthe queue of the node and if there exists an instruction in the queue, apurge instruction with the oldest timestamp (e.g., purge instruction inthe queue is provided in FIFO order) is selected as the next purgeinstruction to be provided.

In some embodiments, determining whether the time value associated withthe next purge instruction is chronologically before the threshold timeincludes determining whether a timestamp of the next purge instruction(e.g., timestamp indicates when the next purge instruction was added tothe queue) is chronologically before the threshold time. In someembodiments, the threshold time is associated with a current time whenthe determination is made. For example, the threshold time is a dynamicvalue determined by subtracting a predetermined amount of a time period(e.g., 5 minutes) from a current time. This may allow verification ofwhether FIFO processing of queued purge instructions has reached a stateof the queue where any purge instruction potentially still waiting inthe queue to be processed has been added to the queue within the lastpredetermined amount of time (e.g., narrowing the amount of purgeinstructions that can remain queued in the queue before the nodetransitions to a transitional state). In some embodiments, the thresholdtime is associated with a time when the node began processing queuedpurge instructions in its queue after becoming unavailable. For example,the threshold time is set as the time when the first purge instructionwas requested from the queue of the node after the node becomeunavailable.

If at 504 it is determined that the next purge instruction exists in thequeue and the time value associated with the next purge instruction ischronologically before the threshold time, at 506, the next purgeinstruction is provided to the requestor. For example, the next purgeinstruction is removed from the queue and provided to the node forprocessing and completion. Once a notification is provided that provideda purge instruction has been successfully completed by the node, theprocess returns to 502.

If at 504 it is determined that the next purge instruction does notexist in the queue or the time value associated with the next purgeinstruction is chronologically not before the threshold time, at 508, anavailability state of the node is indicated as transitional and acurrent time value is stored as a reference time value. For example, astored availability status indicator of the node is updated as“ready-to-become online.” In some embodiments, indicating the statusincludes modifying a data structure of a content distribution managerthat tracks availability state of content distribution nodes of acontent distribution network. For example, a data structure entrycorresponding to the availability state of the node is updated toindicate that the node is in the transitional state. When a node is inthe transitional state, the node may be unavailable to serve/distributerequested content as a part of a content distribution network, butunlike the unavailable state, adding a purge instruction of a purgerequest in its queue without having the transitional state node processand complete the purge instruction does not allow a confirmation to beprovided that the purge request has been processed (e.g., as compared toan unavailable state node where adding the purge instruction to itsqueue would be sufficient). The state entry indicated in 508 may be usedin 306 of FIG. 3 to at least in part determine whether the node is in atransitional state. Determining the reference time may includedetermining a current time when the node is placed in the transitionalstate and recording the current time as the reference time.

At 510, any remaining purge instructions in the queue of the node with atime value chronologically before the reference time is provided forprocessing in chronological order. For example, the node requests a nextpurge instruction from its queue and the next purge instruction isprovided (e.g., in FIFO order of the queue) for processing by the node.The node indicates when it has successfully processed the purgeinstruction. The applicable purge instructions are provided in orderuntil there does not exist any remaining purge instruction in the queuethat has a time value (e.g., timestamp of when the instruction was addedto the queue) before the reference time. Thus the transitional state mayallow a node to process queued purge instructions while not requiringadditional purge instructions added to its queue while the node is inthe transitional state to be completed before the node switches itsavailability state to become available.

At 512, an availability state of the node is indicated as available. Forexample, a stored status indicator of the node is updated as “online” Insome embodiments, indicating the state includes modifying a datastructure of a content distribution manager that tracks availabilitystates of nodes of a content distribution network. For example, a datastructure entry corresponding to the node is updated to indicate thatthe node is available. The state entry indicated in 512 may be used in304 of FIG. 3 to at least in part determine whether the node isavailable.

FIG. 6 is a flowchart illustrating an embodiment of a process forprocessing a purge instruction. The process of FIG. 6 may be at least inpart implemented on one or more of nodes 112, 114, and 116 of FIG. 1. Insome embodiments, the process of FIG. 6 may be performed continuallywhile a node is not unavailable.

At 602, a next purge instruction is requested from a queue of a node. Insome embodiments, the next purge instruction from the queue is the purgeinstruction added to the queue in 204 of FIG. 2. In some embodiments,the request of 602 is received in 502 or 510 of FIG. 5. In the event thenext purge instruction does not exist (e.g., queue is empty), theprocess may end and the process may be repeated (e.g., periodically).

At 604, the next purge instruction is received and processed. In someembodiments, processing the purge instruction includes clearing anindicated content of the purge instruction from a storage/cache of thenode. For example, a cache of the node is cleared of a contentreferenced by a location address specified in the purge instruction. Insome embodiments, processing the purge instruction includesreplacing/refreshing an indicated content of the purge instruction in astorage of the node. For example, a cache of the node is of an indicatedcontent and/or reloaded with a content referenced by a location addressspecified in the purge instruction.

At 606, a confirmation is provided that the purge instruction has beencompleted. For example, the confirmation is provided to a contentdistribution manager (e.g., manager 106 of FIG. 1) to allow the contentdistribution manager to track completion of the purge instruction, anavailability status of the node, and/or when a next purge instructionshould be provided.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A system for processing a purge request,comprising: an interface configured to receive the purge request; astorage configured to store an availability state for each contentdistribution node in a group of content distribution nodes; and aprocessor configured to: generate, based on the purge request, one ormore purge instructions for one or more available state contentdistribution nodes of the group; queue, based on the purge request, oneor more queued purge instructions for one or more unavailable statecontent distribution nodes of the group; determine that the one or moreavailable state content distribution nodes of the group have completedprocessing the one or more purge instructions generated for the one ormore available state content distribution nodes; and authorize, based atleast in part on the queuing of the one or more queued purgeinstructions for the one or more unavailable state nodes, an indicationthat the purge request has been completed.
 2. The system of claim 1,wherein the purge request indicates content to be removed from localcache storages of the group of content distribution nodes.
 3. The systemof claim 1, wherein the purge request indicates content to be replacedfrom local cache storages of the group of content distribution nodes. 4.The system of claim 1, wherein the indication is authorized before theone or more unavailable state nodes completes processing of the one ormore queued instructions.
 5. The system of claim 1, wherein the group ofcontent distribution nodes is included in a content distribution networkthat mirrors content across the content distribution nodes anddistributes the mirrored content.
 6. The system of claim 1, wherein thegroup of content distribution nodes is included in a content deliverynetwork.
 7. The system of claim 1, wherein the request is received froma content provider of content indicated to be purged in the purgerequest.
 8. The system of claim 1, wherein the one or more availablestate content distribution nodes are online and available to distributecontent to a requestor of the content.
 9. The system of claim 1, whereinthe one or more unavailable state content distribution nodes are notavailable to distribute content to a requestor of the content.
 10. Thesystem of claim 1, wherein generating the one or more purge instructionsfor the one or more available state content distribution nodes includesadding the one or more generated purge instructions to purge instructionqueues of the one or more available state content distribution nodes.11. The system of claim 1, wherein the storage is further configured tostore for each content distribution node of the group, a purgeinstruction status for the received purge request.
 12. The system ofclaim 1, wherein the storage is a memory.
 13. The system of claim 1,wherein the indication was authorized based on a verification that theone or more queued purge instructions were queued for the one or moreunavailable state nodes and the determination that the one or moreavailable state content distribution nodes of the group have completedprocessing the one or more purge instructions generated for the one ormore available state content distribution nodes.
 14. The system of claim1, wherein the indication was authorized based at least in part on averification that one or more transitional state content distributionnodes of the group have completed processing one or more purgeinstructions generated based on the purge request.
 15. The system ofclaim 14, wherein the processor is further configured to determine thata specific one of the one or more unavailable state content distributionnodes has requested a next content purge instruction from its purgeinstruction queue and a time value associated with the next purgeinstruction is chronologically after a threshold time, and transitionthe specific one unavailable state content distribution node to become atransitional state content distribution node.
 16. The system of claim15, wherein the threshold time is a dynamic value determined bysubtracting a predetermined amount of time period from a current time.17. The system of claim 15, wherein the processor is further configuredto determine that the transitional state content distribution node doesnot have left processing a purge instruction that was queued before thetransitional state content distribution node was transitioned as thetransitional state content distribution node, and transition thetransitional state content distribution node to become an availablestate content distribution node.
 18. The system of claim 1, whereinauthorizing the indication includes providing the indication to a senderof the purge request that the purge request has been completed.
 19. Amethod for processing a purge request, comprising: receiving the purgerequest; tracking an availability state for each content distributionnode in a group of content distribution nodes; generating, based on thepurge request, one or more purge instructions for one or more availablestate content distribution nodes of the group; queuing, based on thepurge request, one or more queued purge instructions for one or moreunavailable state content distribution nodes of the group; determiningthat the one or more available state content distribution nodes of thegroup have completed processing the one or more purge instructionsgenerated for the one or more available state content distributionnodes; and using a processor to authorize, based at least in part on thequeuing of the one or more queued purge instructions for the one or moreunavailable state nodes, an indication that the purge request has beencompleted.
 20. The method of claim 19, wherein the purge requestindicates content to be removed from local cache storages of the groupof content distribution nodes.
 21. The method of claim 19, wherein thepurge request indicates content to be replaced from local cache storagesof the group of content distribution nodes.
 22. The method of claim 19,wherein the indication is authorized before the one or more unavailablestate nodes completes processing of the one or more queued instructions.23. The method of claim 19, wherein the group of content distributionnodes is included in a content distribution network that mirrors contentacross the content distribution nodes and distributes the mirroredcontent.
 24. The method of claim 19, wherein the group of contentdistribution nodes is included in a content delivery network.
 25. Themethod of claim 19, wherein the request is received from a contentprovider of content indicated to be purged in the purge request.
 26. Themethod of claim 19, wherein the one or more available state contentdistribution nodes are online and available to distribute content to arequestor of the content.
 27. The method of claim 19, wherein the one ormore unavailable state content distribution nodes are not available todistribute content to a requestor of the content.
 28. The method ofclaim 19, wherein generating the one or more purge instructions for theone or more available state content distribution nodes includes addingthe one or more generated purge instructions to purge instruction queuesof the one or more available state content distribution nodes.
 29. Themethod of claim 19, wherein tracking the availability state for eachcontent distribution node includes tracking for each contentdistribution node of the group, a purge instruction status for thereceived purge request.
 30. The method of claim 19, wherein theavailability state for each content distribution node is stored in amemory.
 31. The method of claim 19, wherein the indication wasauthorized based on a verification that the one or more queued purgeinstructions were queued for the one or more unavailable state nodes andthe determination that the one or more available state contentdistribution nodes of the group have completed processing the one ormore purge instructions generated for the one or more available statecontent distribution nodes.
 32. The method of claim 19, wherein theindication was authorized based at least in part on a verification thatone or more transitional state content distribution nodes of the grouphave completed processing one or more purge instructions generated basedon the purge request.
 33. The method of claim 32, further comprisingdetermining that a specific one of the one or more unavailable statecontent distribution nodes has requested a next content purgeinstruction from its purge instruction queue and a time value associatedwith the next purge instruction is chronologically after a thresholdtime, and transitioning the specific one unavailable state contentdistribution node to become a transitional state content distributionnode.
 34. The method of claim 33, wherein the threshold time is adynamic value determined by subtracting a predetermined amount of timeperiod from a current time.
 35. The method of claim 33, furthercomprising determining that the transitional state content distributionnode does not have left processing a purge instruction that was queuedbefore the transitional state content distribution node was transitionedas the transitional state content distribution node, and transitioningthe transitional state content distribution node to become an availablestate content distribution node.
 36. The method of claim 19, whereinauthorizing the indication includes providing the indication to a senderof the purge request that the purge request has been completed.
 37. Acomputer program product for processing a purge request, the computerprogram product being embodied in a tangible non-transitory computerreadable storage medium and comprising computer instructions for:receiving the purge request; tracking an availability state for eachcontent distribution node in a group of content distribution nodes;generating, based on the purge request, one or more purge instructionsfor one or more available state content distribution nodes of the group;queuing, based on the purge request, one or more queued purgeinstructions for one or more unavailable state content distributionnodes of the group; determining that the one or more available statecontent distribution nodes of the group have completed processing theone or more purge instructions generated for the one or more availablestate content distribution nodes; and authorizing, based at least inpart on the queuing of the one or more queued purge instructions for theone or more unavailable state nodes, an indication that the purgerequest has been completed.
 38. The computer program product of claim37, wherein generating the one or more purge instructions for the one ormore available state content distribution nodes includes adding the oneor more generated purge instructions to purge instruction queues of theone or more available state content distribution nodes.
 39. The computerprogram product of claim 37, wherein the indication was authorized basedon a verification that the one or more queued purge instructions werequeued for the one or more unavailable state nodes and the determinationthat the one or more available state content distribution nodes of thegroup have completed processing the one or more purge instructionsgenerated for the one or more available state content distributionnodes.
 40. The computer program product of claim 37, wherein theindication was authorized based at least in part on a verification thatone or more transitional state content distribution nodes of the grouphave completed processing one or more purge instructions generated basedon the purge request.